How severe is CVE-2020-24659?

CVE-2020-24659 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2020-24659 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 4% (89th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-24659?

CVE-2020-24659 primarily affects Gnu Gnutls. In total, 6 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2020-24659?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2020-24659 published?

CVE-2020-24659 was published on 2020-09-04 and last updated on 2026-06-17.

CVE-2020-24659

CVE-2020-24659 is a high-severity vulnerability in Gnu Gnutls with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-476.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 4% (89th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-476
Affected product: Gnu Gnutls
Published: 2020-09-04
Last modified: 2026-06-17

Description

An issue was discovered in GnuTLS before 3.6.15. A server can trigger a NULL pointer dereference in a TLS 1.3 client if a no_renegotiation alert is sent with unexpected timing, and then an invalid second handshake occurs. The crash happens in the application's error handling path, where the gnutls_deinit function is called after detecting a handshake failure.

Frequently asked questions

What is CVE-2020-24659?: An issue was discovered in GnuTLS before 3.6.15. A server can trigger a NULL pointer dereference in a TLS 1.3 client if a no_renegotiation alert is sent with unexpected timing, and then an invalid second handshake occurs. The crash happens in the application's error handling path, where the gnutls_deinit function is called after detecting a handshake failure.
How severe is CVE-2020-24659?: CVE-2020-24659 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2020-24659 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 4% (89th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-24659?: CVE-2020-24659 primarily affects Gnu Gnutls. In total, 6 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2020-24659?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2020-24659 published?: CVE-2020-24659 was published on 2020-09-04 and last updated on 2026-06-17.

References

Affected products (6)

cpe:2.3:a:gnu:gnutls:*:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
cpe:2.3:o:opensuse:leap:15.1:*:*:*:*:*:*:*
cpe:2.3:o:opensuse:leap:15.2:*:*:*:*:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:20.04:*:*:*:lts:*:*:*

More vulnerabilities in Gnu Gnutls

CVE-2008-1948 — Critical (CVSS 10.0): The _gnutls_server_name_recv_params function in lib/ext_server_name.c in libgnutls in gnutls-serv in GnuTLS before…
CVE-2021-20232 — Critical (CVSS 9.8): A flaw was found in gnutls. A use after free issue in client_send_params in lib/ext/pre_shared_key.c may lead to memory…
CVE-2021-20231 — Critical (CVSS 9.8): A flaw was found in gnutls. A use after free issue in client sending key_share extension may lead to memory corruption…
CVE-2017-5337 — Critical (CVSS 9.8): Multiple heap-based buffer overflows in the read_attribute function in GnuTLS before 3.3.26 and 3.5.x before 3.5.8…
CVE-2017-5336 — Critical (CVSS 9.8): Stack-based buffer overflow in the cdk_pk_get_keyid function in lib/opencdk/pubkey.c in GnuTLS before 3.3.26 and 3.5.x…
CVE-2017-5334 — Critical (CVSS 9.8): Double free vulnerability in the gnutls_x509_ext_import_proxy function in GnuTLS before 3.3.26 and 3.5.x before 3.5.8…

All CVEs affecting Gnu Gnutls →

Other CWE-476 (NULL Pointer Dereference) vulnerabilities

CVE-2022-36648 — Critical (CVSS 10.0): The hardware emulation in the of_dpa_cmd_add_l2_flood of rocker device model in QEMU, as used in 7.0.0 and earlier,…
CVE-2020-14500 — Critical (CVSS 10.0): Secomea GateManager all versions prior to 9.2c, An attacker can send a negative value and overwrite arbitrary data.
CVE-2010-2495 — Critical (CVSS 10.0): The pppol2tp_xmit function in drivers/net/pppol2tp.c in the L2TP implementation in the Linux kernel before 2.6.34 does…
CVE-2026-46195 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: smb: client: validate dacloffset before building…
CVE-2026-31657 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: batman-adv: hold claim backbone gateways by…
CVE-2026-31436 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: dmaengine: idxd: fix possible wrong descriptor…

Browse all CWE-476 (NULL Pointer Dereference) vulnerabilities →